1. Field of the Invention
The present invention relates to a modular engine design for a family of internal combustion engines and particularly, to a family of four-stroke engines.
2. Description of the Related Art
In developing a new engine, significant resources go into designing a basic cylinder package. In an overhead valve (“OHV”) four-stroke engine, the basic cylinder package includes the cylinder itself, the cylinder head, valve train, piston, connecting rod and related components. These components must be designed to provide the desired engine displacement, performance, durability, size and weight at an acceptable manufacturing cost. Therefore, in a multiple cylinder engine, some or all of these components are designed for one cylinder and are then utilized in the other cylinders in the multiple cylinder engine. For instance, it is common in an automotive engine for the pistons, connecting rods, intake valve mechanisms and exhaust valve mechanisms to be identical from cylinder to cylinder within the 4, 5, 6 and 8 cylinders of that engine.
However, such a common parts package is not known in the automotive field to have been adopted by manufacturers in a family of engines of different basic configurations. For instance, in the automotive field it is not known to use the common parts package in both a V-8 engine and an inline four or six cylinder engine. When a manufacturer offers, for example, both a V-8 engine and an inline (or straight) six, each of these engines is typically independently developed from the ground up, with little parts interchangeability. This increases not only the designing cost but also the cost of manufacturing, storing and distributing this greater number of unlike components.
The use of common cylinder package components in different engine configurations has been previously accomplished in the motorcycle field. In the 1950's, the Vincent motorcycle company manufactured the Rapide, a 1000 cc OHV V-twin, and the Meteor, a 500 cc OHV single. The Meteor used the same cylinder, piston, piston rings, piston pin and connecting rod as used in both cylinders of the Rapide. The Meteor also used the same cylinder head as was used on the front cylinder of the Rapide, although the rear cylinder head on the Rapide differed from the front cylinder head. The valve trains were the same on the single cylinder of the Meteor and both cylinders of the Rapide, but for the camshafts. The Meteor camshaft was the same as the rear camshaft of the Rapide, while the rear camshaft of the Rapide differed from the front camshaft of the Rapide. Thus, even though there was some commonality of top end components between the single and the V-twin, overall commonality was not achieved on all cylinders of these engines as evidenced, for example, by the different cylinder heads installed on the front and rear cylinders of the V-twin. Further, there was no use of the common cylinder package on any other configuration of engine. Rather, the V-twin was basically the single configuration with an added cylinder.
Further, even when there has been commonality of components within different engines, those engines were all intended for similar use applications. For instance, even though the Vincent Rapide and Meteor motorcycles used common components in their respective engines, both engines were intended specifically for use in motorcycles and were subjected to the same or very similar operating environments. Likewise, even where an automobile manufacturer has used common components in various engines, such engines have been intended for the same application, i.e., powering an automobile or truck. Consideration has not been given to designing common components for a plurality of engines intended for quite diverse applications, such as for use in watercraft, boats (both inboard and outboard applications), snowmobiles, ATVs and motorcycles, all of which place different demands on their respective engines.